1. Field of the invention
The present invention relates to a laminated structure formed of a ceramic color layer and a conductive layer, formed on a windshield (made of plate glass) for cars.
2. Description of the prior art
On some rear windshields of automobiles, bus bars for defogging and slender hot wires extending between the bus bars are formed. These bus bars and hot wires are conductive layers formed on the glass surface by printing a silver paste on the interior surface of the windshield of cars followed by melting to give adhesion. The bus bars, which are broad, are very conspicuous when viewed from the exterior side of cars. Now, for the purpose of concealing the bus bars from the exterior side of cars, it has been practiced to form as shown in FIG. 5 a ceramic color layer 101 on the peripheral edge of a windshield 100 and between the windshield 100 and a bus bar 102.
To form the bus bar 102 on the ceramic color layer 101 as stated above, the ceramic color layer 101 is first printed on the windshield 100 and thereafter the color layer 101 is dried or cured. Next, a silver paste is printed on the ceramic color layer 101 and thereafter the silver paste is dried or cured. Then the ceramic color layer 101 and the silver paste are simultaneously melted to give adhesion, i.e., fired, at a high temperature caused when the windshield 100 is formed to have a bend. In general, the above ceramic color layer 101 is so prepared that it may contain after firing, 55 to 90 wt. % of frit and 10 to 45wt. % of a pigment.
However, at the time when the above ceramic color layer 101 and silver paste are simultaneously fired on the windshield, silver ions in the silver paste tend to diffuse and migrate through the frit in the ceramic color layer 101 and reach the interior surface of the windshield of cars to cause ionic color formation 103. This ionic color formation can be visually recognized from the exterior side of cars, resulting in a deterioration in the appearance of the windshield 100.
Taking account of the above problems involved in the laminated structure formed of the ceramic color layer and the conductive layer, the present invention was so made that these problems can be effectively solved.